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A nice thing about requiring a vDSO is that it makes it incredibly easy to provide full support for running 32-bit processes on 64-bit systems. Instead of letting the kernel be responsible for composing/decomposing 64-bit arguments across multiple registers/stack slots, all of this can now be done in the vDSO. This means that there is no need to provide duplicate copies of certain system calls, like the sys_lseek() and freebsd32_lseek() we have for COMPAT_FREEBSD32. This change imports a new vDSO from the CloudABI repository that has automatically generated code in it that copies system call arguments into a buffer, padding them to eight bytes and zero-extending any pointers/size_t arguments. After returning from the kernel, it does the inverse: extracting return values, in the process truncating pointers/size_t values to 32 bits. Obtained from: https://github.com/NuxiNL/cloudabi
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